Biology chapter 5

To understand photosynthesis, you will need to know about some properties of sunlight nergy. The energy that undulates across space like waves moving across a sea. The distance between ecach wave is called....wavelengths

Pigments

are molecules that capture light energy. They are the key molecular bridges from sunlight to photosynthesis. Each kind of pigmjent can absorb only specific wavelengths of light. All other wavelengths arenot absorbed, but instead are rasnmitted through the molecule or reflected by it.

Chlorophyll a

the primary pigment in almost all photoautotrophs, chlorophyll absorbs mainly red and blue-violet light. It reflects all other light-which is mainly green. That is why plants have that have a lot of chlorophyll appear intensely green.

Chlorophyll b

reflects green and yellow ligh, so it is yellow-green. Red, orange, and yellow carotenoids impart color to some flowers, fruits, and vegetables.

Xanthophylls

may be yellow, brown, purple, or blue.

Anthocyanins

color some red or purple flowers and foods, including cherries, blueberries, and rhubarb. Accessory pigments are masked by green chlorophylls in the leaves of many plants until autmn.

Phycobilins,

which are red or blue-green, are th signature pigments of red algae and cyanobacteria. A few prokaryotes of ancient lineages still use unusual pigments like the intensely purple bacteriorhodopsin.

Light-dependent reactions

In the first stage, sunlight energy is converted to chemical bond energy of ATP. Water molecules are split, and typically the coenzyme NADP+ picks up the released hydrogen and electrons thus becoming NADPH.

Light-independent reactions

the second stage, runs on energy donated by the ATP. Glucose and other carbohydrates are made with carbon and oxygen atoms (secured from carbon dioxide and water), and with the hydrogen and electrons delived by NADPH.

Chloroplasts

Inside chloroplasts the organelles of photosynthesis in all plants and certain protists. A chloroplast has a semifluid interior, called the stroma, enclosed by two other membranes.

Thylakoid membrane

A third membrane forms a compartment inside the stroma. It folds back on itself into what often look like stacks of pancakes (thylakoids) connected by channels. The space inside the folds is one continuous compartment. The light-dependent reactions occur at the thylakoid membrane, and sugars are built in the stroma

photosystems

or reaction center, are arrays of hundreds of pigments and other molecules. chloroplasts have two tuypes, called 1 and 11. each photosystem is surrounded by hundreds of light harvesting complexes.

ATP synthases

a type of active transport protein. the flow of hydrogen ions through atp synthases powers the attachment of phosphate groups to ADP molecules in teh stroma. in this ways, atp forms.

Calvin Benson cycle

sugars form in this cycle. a pathway that runs inside the stroma of chloroplasts. the cycle also called light independent bedcause light is not needed to run the reaction. it uses the atp and nadph that formed in the light dependent reacitons. plants get their carbon and oxygen buil.ding blocks from carbon dioxide in the air.

rubisco

the enzyme rubisco joins a carbon from CO2 tio five carbon ribulose bisphosphate... the resulting unstable intermediate is the molecules that starts the calvin benson cycle.

carbon fixation

the process of securing carbon from the environment by incorporating it into a stable organic compound is called carbon fixation

stomata

a waxy cuticle stops water loss from leaves. water and gases move into and out of leaves only across tiny openings called the stomata. stomata close on hot, dry days, so water and O2 do not exit leaves and CO2 does not enter them. Plants cannot make as much sugar when their photosynthetic cells are exposed to too much O2 and too little Co2

C4 plants

four carbon oxaloacetate forms first in reacitons that run through two cell types. in mesophyll cells, the c4 cycle will fix carbon no matter how much o2 there is. c4 plants use more atp than c3 plants do because they have to fix carbon twice, but tehy can make more sugar on dry days

c3 plants

don't grow well without irrigation in hot, dry climates. their name is a nod to the three carbon PGA, the first stable intermediate for form during the calvin benson cycle.. when oxygen builds up in c3 leaves, rubisco binds oxygen, not CO@. this alternate reaction yields co2 so the plant loses carbon instead of fixing it.

CAM plants

open stomata at night and fix carbon by repeated turns of a C4 cycle, and then the calving benson cycle runs on the next day. camp stand for crassulacean acid metabolism. these plants include cacti, and other succulents, which have juicy water storing tissues and thick surface layers. both are adaptations to hot, dry climates. some camp plants usrvive prolonged droughts by closing their stomata even at night.